Ever wonder what makes the Ring of Fire, the Ring of Fire? Mary, Peter, and Daniel did. Join them as they discover the answer in today’s Secret Science Society adventure!
Peter and Mary were not jealous of much, but they looked at the pictures from Daniel’s vacation to Colorado with envy. While they had stayed at home over spring break, Daniel’s family had gone to the mountains to ski. And the first day back at school, he showed pictures from the trip to Mary and Peter over lunch.
“I can’t believe that it is so snowy there!” Mary said.
“Yeah,” Peter added. “And the mountains are so tall! Is it really a mile high there?”
“Yes, it is,” Daniel replied. “There’s even a step on the capitol building that tells you when you are a mile above sea level.”
“Cool! I wonder what made the mountains?” Mary asked.
“I don’t know, but I know who will,” Peter said.
“Mr. Medes!” all three chorused.
“Let’s go ask him!” Mary said.
The three friends cleared their lunch trays and then went down the hall to Mr. Medes’ classroom.
“Ah! A salubrious spring to you!” Mr. Medes greeted them. “What brings three such avid explorers to my room on a bright, sunny day?”
“We were looking at pictures of the mountains in Colorado,” Daniel said. “And we wondered what makes mountains.”
“That happens to be an excellent question!” Mr. Medes replied. “Would you believe me if I told you that grandparent’s didn’t know the answer but we do?”
As the three friends shook their heads, he went to the supplies cabinet and brought out two sheets of paper and a shaker of salt. He put the paper on the table, forming an “X”, and then spread a layer of salt about an inch thick over one side of the X.
“It is true,” Mr. Medes continued. “Until very recently, we thought that the surface of the Earth was just one big piece and stuck in one place. But then we discovered that it is broken into more than a dozen smaller pieces that move around very slowly. Those pieces are called”
“Plates!” Peter interrupted. “And they float on magma!”
“Well, you are right about them being called plates,” Mr. Medes replied. “But they don’t float on magma. Magma is molten rock and the outer part of the Earth is solid. But it oozes under pressure, sort of like bubble gum or fudge, which is why those plates can move around5r.”
“Oh. I guess the movies got that bit wrong,” Peter said, abashed.
“Movies usually do,” Mr. Medes smiled. “But as those plates glide along on the outer part of the Earth, which we call the mantle, they either move apart from each other, move beside each other, or run into each other. Now what I’ve done here is create a model that we can use to simulate how those plates move. Here’s how we’ll do the experiment. Daniel, you’ll hold the piece of paper that is on the top so that it cannot move. Mary, you’ll pull on the far side of the piece of paper that is underneath, so that it moves toward the other piece of paper. So those two pieces of paper are two plates moving on the outside of the Earth and that salt on top is like the crust of the Earth and will move with the plates. Got it?”
Seeing everyone nod, he continued. “Now what we have to do is to predict what will happen when the bottom plate runs into the top plate. Peter, what do you think will happen?”
“The sediment will stay in one place and slide off of the plate,” Peter replied.
“No,” Mary said. “You are wrong. The sediment will go under the top plate.”
“I don’t think that will happen,” Daniel said. “I think that the sediment will get scrunched up.”
Well, there’s only one way to find out,” Mr. Medes said. “Let’s move the plates!”
What do you think will happen? Do the experiment!
As Daniel held the paper on top still, Mary slowly pulled the bottom paper. As the far side of the “X” got longer, the other side got shorter, and the salt began to move together. At first, it didn’t look as if anything was happening. And then, as the three experimenters watched, the salt began to pile up and make hills and mountains.
“Wow!” Peter exclaimed. “The salt did pile up!”
“That’s right,” Mr. Medes said. “And that is the secret to orogeny, or mountain building. As the plates move together, the sediment gets squished up to form a great big mountain. Almost every large mountain chain was formed this way; the Himalayas, the Rockies, the Andes, the Alps all were made when one plate crashed into another.”
“And Hawai’i, too?” Mary asked.
“Actually, Hawai’i is a special case, just like Iceland and Yellowstone” Mr. Medes replied. “It was formed a different way, when a big blob of magma hit the bottom of the plate and melted its way through. And then there is the longest mountain chain in the world, the Mid-Atlantic ridge. It was formed when plates moved apart. But those are exceptions. The rule is that mountains are made when two plates crash together, just as most dents are made when two cars crash.”
“Gosh,” Daniel said. “So I was standing an old accident site!”
“Actually, the crash that made the Rocky mountains is still going on,” Mr. Medes replied. “The plates are still moving around. The Rockies were formed when the North American plate hit the Farallon plate. Normally, you’d get the mountains made very close to the coast, like the Cascades, the Aleutians and the Andes. But, because the Farallon plate went under the North American plate at such a shallow angle, it made the mountains very far inland.”
“Don’t the Cascade mountains and the Aleutians have lots of volcanoes?” Mary asked.
“Yes, they do!” Mr. Medes said. “And that is because of those plates. You remember how you predicted that the sediment would go down with the plate?”
“Yes,” Mary said. “I guess I was wrong.”
“Not entirely,” Mr. Medes replied. “Though most of the sediment stays up on the surface, some gets stuck on the plate and moves down into the mantle. And that sediment is chock full of water and limestone. When the sediment gets into the mantle, it releases that water and the carbon dioxide from the limestone. That gets into the surrounding mantle rocks and makes them melt, just a little. That new, hot magma goes up and erupts on the surface as a volcano. That’s why there are so many volcanoes around the Pacific rim and why we sometimes call it the ‘ring of fire’.”
At that moment the bell rang, signaling that it was time for class.
“Speaking of ringing,” Daniel said. “It is time for class. See you guys later!”